OBSERVATIONS AND CORRESPONDENCE. 



Dr. Weismann's Theory of Heredity. 



I have received the following interesting observations from Dr. E. Sickenberger, 

 Professor of Chemistry, Botany, and Materia Medica in the School of Medicine, Cairo, 

 which readers interested in the subject may be glad to see : — " I have read with great 

 interest your publication upon Dr. Weismann's theory, and I am very glad to see 

 that your conclusions are entirely in accordance with my own observations. I 

 believe, if Weismann had had more special knowledge of botanical matters, he would 

 not have undertaken to apply his theory to plants. You have completely refuted by 

 your explanations his assertion that a continuity of germ-plasm exists in a certain 

 series of somatic cells only. I cannot admit any essential difference of characters 

 between species and varieties, such being only due to a greater or less degree of 

 qualities acquired by the influence of external conditions during a longer or shorter 

 period. Hybridisation comes in, in a secondary way, mixing those acquired qualities 

 with another series. Hereditary persistence is, I believe, nothing else than the 

 maintenance of those acquired qualities under the power of inertia (Gesetz derTragheit) . 

 The more any acquired qualites have changed the anatomical and chemical consti- 

 tution of a plant, so much the more will those qualities be persistent. If Weismann 

 says ' acquired characters cannot be transmitted at all,' every day in Egypt contradicts 

 this opinion, and the fact that ' species of plants in Egypt have remained unchanged 

 for thousands of years,' only proves that the climatal conditions of Egypt have 

 remained all the time unchanged. On the other hand, seeds of Gigniit [?] , a variety of 

 Cannabis sativa from Europe, produce the true Cannabis saliva yarn by the third 

 generation. Black mustard, Brassica {Sinapis) nigra is transformed in the second 

 generation into the endemic B. bracteolata, Fisch. et Mey. [Plante particuliere a 

 I'Egypte (Asch. et Schweinf.)], and the thick-rooted celery assumes in the first year 

 the much foliated form with a thin root-stock, like the summer spontaneous form of 

 Egypt. I have myself had the opportunity of substantiating these facts several, 

 times. On the other hand, it must be proved that external influences act in some 

 other way upon the germ-plasm than upon the somato-plasm — all action in nature 

 being based upon the universal physical and chemical forces— so that really the 

 constitution of the pretended germ-plasm is different from that of the somato-plasm." 



George Henslow. 



TO CORRESPONDENTS. 



A II communications for the Editor to be addressed to the Editorial 

 Offices, 67-69 Chancery Lane, London, W.C. 



J. Wilson {Stamford). — The Conchological Society's List of British Land and 

 Freshwater Mollusca has already appeared : see Journ. Conchology for April, 1892. 



W. H. Corder [Lancaster). — The Darwin collection of Cirripedia is now in the 

 British Museum, but we believe that all the duplicates are to be seen in the 

 Liverpool Museum. The " Coromilites diadema " to which you refer is also in the 

 British Museum. The Parkinson sale took place in 1826, and the specimens were 

 widely distributed ; this specimen, however, finally reached the national collection 

 through a Bury-St. -Edmunds collector. 



